Vibrations are a common problem in many machines comprising reciprocating or rotating parts. Vibrations occur for instance in internal combustion engines or in the auxiliaries of them, such as in turbochargers. Vibrations can be reduced by modifying the components, for instance by increasing the stiffness of some parts of the structure. However, this is not always possible or practical for instance because of cost-efficiency reasons. Therefore, different vibration dampers have been developed for reducing vibrations of machines or machine parts. A vibration damper can be implemented as a tuned mass damper, an adaptive tuned mass damper, a semi active damper, or an active damper. A typical mass damper comprises a spring-supported movable mass that can move in a space that is filled with a damping medium, such as gas or liquid. The kinetic and pressure energy of the damping medium is converted into thermal energy and the motion of the mass element and thus also the vibration of the component to which the mass damper is attached is dampened. In a tuned mass damper the tuning frequency cannot be adjusted during use, whereas in an adaptive tuned mass damper the tuning frequency can be adjusted also during use. Adaptive tuned mass dampers can thus be used to dampen vibrations caused by different modes of vibration. In active dampers external force is produced instead of or in addition to the vibrations of the mass element.
Patent FI 117573 B discloses a mass damper comprising a vibration element being arranged inside a chamber that is filled with damping medium, such as gas or liquid. The vibration element is supported by springs to the ends of the chamber and can reciprocate in the direction of a linear guide that is arranged inside the chamber. The vibration element consists of several parts for enabling easier adjustment of the mass damper. Also the damping medium flow in the damper can be adjusted for changing the damping properties. Although the damping properties of the mass damper disclosed in patent FI 117573 B can be adjusted to some extent, changing of the tuning frequency is not possible during the use of the damper.